The present invention relates to photosensitive resin compositions (resists) suitable for minute-processing of semiconductors by using ultraviolet rays or far-ultraviolet rays (including excimer laser and so on), a method for producing the same, and a method for forming patterns using the same.
There have been known compositions comprising an alkali-soluble novolak resin and a diazonaphthoquinone derivative as resists for semiconductors. These photosensitive resin compositions have been used as positive resists utilizing the characteristic that a diazonaphthoquinone group is decomposed upon irradiation with a light of 300 to 500 nm wavelength to form a carboxyl group, allowing the compositions to change from an alkali-insoluble state to an alkali-soluble state.
On the other hand, with a rise in the integration level of integrated circuits of semiconductors, the integrated circuits are getting minuter and minuter in recent years, and the formation of patterns in submicron order, quartermicron order, and smaller is now demanded. The most conventional method for achieving miniaturization or minuter integrated circuits is to use an exposure light of a shorter wavelength. For example, instead of using g-line (wavelength: 436 nm) or i-line (wavelength: 365 nm) of high-pressure mercury lamps generally used, a light source of a shorter wavelength such as KrF excimer laser (wavelength: 248 nm) and ArF excimer laser (wavelength: 193 nm) of next generation have already come into practical use.
However, the use of novolak resin/diazonaphthoquinone-type positive resists having been employed for the production of semiconductor integrated circuits using g-line or i-line leads to considerable deterioration in sensitivity and resolution even with KrF excimer laser or ArF excimer laser owing to the absorption ability of the novolak resin. Therefore, the novolak resin/diazonaphthoquinone-type positive resists are lacking in practicability.
Moreover, minute processing with KrF or ArF excimer laser has a number of technical problems to be solved with respect to the choice of, for example, light sources, exposing devices such as a lens system and photosensitive materials (resists). In addition, plant investment for applying the minute processing with KrF or ArF excimer laser to the practical production of semiconductors will be a vast sum of money.
Accordingly, an object of the present invention is to provide a photosensitive resin composition capable of largely improving sensitivity and resolution even with an existing apparatus (particularly, exposing system), a method for producing the same, and a method for forming patterns.
Another object of the present invention is to provide a photosensitive resin composition capable of largely improving the pattern profile and the focus latitude, a method for producing the same, and a method for forming patterns.
The inventors of the present invention made intensive investigations and found that the surface of a resist layer can be made hardly soluble or readily soluble by exposing the resist layer to a light of wavelength xcex1 or xcex2 through a mask patternwiese, the resist layer being composed of a combination of a first photoactive ingredient active at an absorption wavelength xcex1 and a second photoactive ingredient which shows high absorption at wavelength xcex2, and then exposing all over the patterned surface to a light of wavelength xcex2 or xcex1 (hereinafter, referred to simply as xe2x80x9coverall-exposurexe2x80x9d), and that a pattern having a high xcex3-value and high resolution can be formed with high precision by developing the resist layer. The present invention has been achieved based on the above findings.
To summerize, the photosensitive resin composition of the present invention comprises a base resin and a photoactive component, and the photoactive component is constituted of a plurality of photoactive ingredients each having an absorption range at wavelength xcex1 or xcex2, the wavelengths thereof being different from each other. The base resin may be a novolak resin or polyvinylphenol-series polymer, and the photoactive component comprises a first photoactive ingredient having an absorption range at wavelength xcex1 and a second photoactive ingredient having an absorption range at wavelength xcex2. Usually, between the first and second photoactive ingredients, one of which is substantially inert at the absorption wavelength of the other. The first photoactive ingredient and the second photoactive ingredient may be a combination of, for example, a diazobenzoquinone derivative and/or diazonaphthoquinone derivative with an azide compound, a photoactive acid generator, or a photoactive acid generator and a crosslinking agent, or a combination of an azide compound and a photoactive acid generator.
The present invention includes a method for producing photosensitive resin compositions which comprises mixing a base resin with a plurality of photoactive ingredients each having an absorption range at wavelength xcex1 or xcex2, the wavelengths thereof being different from each other.
The present invention further includes a method for forming a pattern which comprises exposing the photosensitive resin composition to a light having a wavelength of either xcex1 or xcex2 to form a pattern, and exposing the entire surface of the pattern-exposed photosensitive resin composition to a light of the other wavelength.
In the present specification, xe2x80x9cphotoactive ingredientsxe2x80x9d are components generally referred to as photosensitizers, sensitizers, and so on, and are components which cause photoreactions by being activated or excited by light and take part in the formation of patterns. Regarding the photoactive ingredients, the term xe2x80x9cwavelengthxe2x80x9d or xe2x80x9cabsorption wavelengthxe2x80x9d xcex1 or xcex2 means a wavelength at which the photoactive component is photosensitized and activated or excited by irradiation of a light of wavelength xcex1 or xcex2 and partakes in a photoreaction. Moreover, in the present specification, the term xe2x80x9cabsorption rangexe2x80x9d of a photoactive ingredient means an absorption wavelength range within which the absorption coefficient is not less than 1 (preferably not less than 10) at an exposing wavelength. The above xe2x80x9cwavelengthxe2x80x9d or xe2x80x9cabsorption wavelengthxe2x80x9d xcex1 or xcex2 refers to an absorption range of the longest wavelength among the above absorption ranges.
The species of the base resin can be selected according to which type of resist, positive or negative, is to be formed, and there may be exemplified phenol novolak resins, polyvinylphenol-series polymers, polymers having a non-aromatic ring such as a cycloalkyl group, polyvinyl alcohol-series polymers, acrylonitrile-series polymers, acrylamide-series polymers, polymers having a photodimerizable functional group such as cinnamoyl group and cinnamylidene group, nylon- or polyamide-series polymers, and polymerizable oligomers. When utilizing as a resist for semiconductor production, a novolak resin, a polyvinylphenol-series polymer and the like can be utilized as the base resin.
As the novolak resin, an alkali-soluble novolak resin is usually employed. When utilizing as a resist for semiconductor production, novolak resins conventionally employed in the field of resist can be used. A novolak resin can be obtained by condensing a phenol having at least one phenolic hydroxyl group in the molecule with an aldehyde in the presence of an acid catalyst. Examples of the phenol are, for example, C1-4alkylphenols such as phenol, o-, m-, and p-cresols, 2,5-, 3,5-, and 3,4-xylenols, 2,3,5-trimethylphenol, ethylphenol, propylphenol, butylphenol, 2-t-butyl-5-methylphenol; dihydroxybenzenes; and naphthols. Examples of the aldehyde are aliphatic aldehydes such as formaldehyde, acetaldehyde, and glyoxal; and aromatic aldehydes such as benzaldehyde and salicylaldehyde.
These phenols can be used either singly or as a combination of two or more species, and the aldehydes can also be used singly or in combination. As the acid catalyst, there may be exemplified inorganic acids (e.g., hydrochloric acid, sulfuric acid, phosphoric acid), organic acids (e.g., oxalic acid, acetic acid, p-toluenesulfonic acid), and organic acid salts (e.g., divalent metal salts such as zinc acetate). The condensation reaction can be carried out according to a conventional method, e.g., at a temperature of about 60xc2x0 C. to 120xc2x0 C. for about 2 to 30 hours. The reaction may be conducted without a diluent or in a suitable solvent.
Any polyvinylphenol-series polymer can be used as the polyvinylphenol-series polymer provided that a vinylphenol is contained therein as a constitutive unit, and it may be a homopolymer or copolymer of a vinylphenol or a derivative thereof, or a copolymer with other copolymerizable monomer. The polyvinyl phenol-series polymer is preferably used with part of or all the phenolic hydroxyl groups contained therein protected by protecting groups. As the protecting groups, there may be mentioned, for example, alkyls (e.g., C1-6alkyl groups, preferably C1-4alkyl groups); cycloalkyl groups (e.g., cyclohexyl group); aryl groups (e.g., 2,4-dinitrophenyl group), aralkyl groups (e.g., benzyl groups that may have a substituent, such as benzyl group, 2,6-dichlorobenzyl group, 2-nitrobenzyl group, and triphenylmethyl group); tetrahydropyranyl group; non-polymerizable acyl groups [e.g., aliphatic acyl groups such as acetyl, propionyl, isopropionyl, butyryl, and isovaleryl groups (preferably, C2-6acyl groups, particularly C2-4aliphatic acyl groups); aromatic acyl groups such as benzoyl group (particularly, C7-13aromatic acyl groups, and the like), and alicyclic acyl groups such as cyclohexylcarbonyl group]; alkoxycarbonyl groups (e.g., C1-6alkoxy-carbonyl groups such as a t-butoxycarbonyl group); aralkyloxycarbonyl groups (e.g., benzyloxycarbonyl group); carbamoyl groups that may have a substituent (e.g., C1-6alkyl groups, C6-14aryl groups) (e.g., carbamoyl, methylcarbamoyl, ethylcarbamoyl, phenylcarbamoyl groups); diC1-4alkylphosphynothioyl groups; and diarylphosphynothioyl groups. The preferred protecting groups include alkyl groups, non-polymerizable acyl groups (particularly, aliphatic acyl groups), alkoxycarbonyl groups, and carbamoyl groups that may have a substituent.
The proportion of the protecting groups contained in the polyvinylphenol-series polymer is, for example, about 10 to 100 mole % and preferably about 20 to 70 mole % (e.g., 20 to 50 mole %), relative to the hydroxyl groups contained in the polymer.
The molecular weight of the polyvinylphenol-series polymer is not particularly restricted and can be selected from within the range of, for example, a weight average molecular weight of about 1,000 to 50,000 and preferably about 2,000 to 30,000 (e.g., 5,000 to 10,000).
The present invention is characterized in that a photoactive component is constituted of a plurality of photoactive ingredients each having an absorption range at wavelength xcex1 or xcex2, the wavelengths thereof being different from each other, and the photoactive component may be constituted of a first photoactive ingredient having an absorption range at wavelength xcex1 and a second photoactive ingredient having an absorption range at wavelength xcex2. Particularly, between the first and the second photoactive ingredients, it is advantageous that one ingredient is substantially inert at the absorption wavelength of the other and not involved in a photoreaction. Usually, the second photoactive ingredient does not show any absorption or is substantially inert at the absorption wavelength of the first photoactive ingredient. It is desirable that the first photoactive ingredient does not show any absorption, or is substantially inert at the absorption wavelength of the second photoactive ingredient. Moreover, although the absorption wavelength xcex1 of the first photoactive ingredient and the absorption wavelength xcex2 of the second photoactive ingredient can be selected according to the wavelength of the light source, it is usually advantageous that the difference between the absorption wavelengths is 30 to 450 nm, preferably about 50 to 400 nm, and more preferably about 70 to 350 nm. Further, when utilizing a conventional and practical exposure system, it is advantageous that the difference between the wavelengths xcex1 and xcex2 is about 100 to 300 nm (e.g., 100 to 280 nm).
One of the first photoactive ingredient and the second photoactive ingredient usually has an absorption wavelength xcex1 of 300 to 550 nm and preferably about 320 to 530 nm (e.g., 350 to 450 nm), and the other one usually has an absorption wavelength xcex2 of about 100 to 350 nm and preferably about 120 to 320 nm (e.g., 150 to 300 nm). The absorption wavelength of the second photoactive ingredient in many cases is shorter than that of the first photoactive ingredient. The absorption wavelength xcex1 of the first photoactive ingredient may usually be selected from within the range of about 300 to 550 nm, and the absorption wavelength xcex2 of the second photoactive ingredient may usually be selected from within the range of about 100 to 350 nm.
Moreover, to prevent a photoreaction from occurring deep down a photosensitive layer (resist film or layer) caused by overall exposure at wavelength xcex1 or xcex2 and allow the surface to absorb the light of xcex1 or xcex2, it is advantageous that a photoactive ingredient which is activated by the light for overall exposure (exposing the entire surface of the resist film or layer) has a high absorption constant at the wavelength of the exposure light. The molecular extinction coefficient xcex5 of the second photoactive ingredient at wavelength xcex1 or xcex2 is usually about 1xc3x97103 to 5xc3x97105, preferably about 5xc3x97103 to 3xc3x97105, and more preferably about 1xc3x97104 to 3xc3x97105.
The first photoactive ingredient and the second photoactive ingredient can be selected, according to the type of the photosensitive resin (positive or negative), from conventional photosensitizers and sensitizers, such as diazonium salts (diazonium salts, tetrazonium salts, polyazonium salts); quinonediazides (e.g., diazobenzoquinone derivatives, diazonaphthoquinone derivatives); azide compounds; pyrylium salts; thiapyrylium salts; photodimerization sensitizers or photopolymerization initiators [e.g., ketones (anthraquinone, benzophenone, or derivatives thereof), benzoin ether or derivatives thereof]; and acid generators.
When utilizing as a positive photosensitive resin (particularly, a resist for semiconductor production), the first and second photoactive ingredients can be selected, according to the species of the photosensitive resin and the absorption ranges of patternwise exposure and overall exposure, from the above-mentioned photosensitizers and sensitizers (particularly, quinonediazides such as diazobenzoquinone and diazonaphthoquinone; azide compounds; acid generators; and the like) as a suitable combination. To be more concrete, when employing a novolak resin as the base resin, the first photoactive ingredient can be constituted of, for example, a diazobenzoquinone derivative and/or a diazonaphthoquinone derivative, and the second photoactive ingredient can be constituted of, for example, an azide compound, a photoactive acid generator, or a photoactive acid generator and a crosslinking agent. A compound that shows high absorption at wavelength xcex1 or xcex2 (i.e., large absorbance at xcex1 or xcex2) is useful as the second photoactive ingredient.
Though either o- or p-quinonediazide may be used as the diazobenzoquinone derivative or the diazonaphthoquinone derivative, o-quinonediazide (ortho-body) is usually employed. The diazobenzoquinone derivative can be obtained by a reaction of 1,2-benzoquinone -4-sulfonyl with a hydroxyl group-containing compound, and the diazonaphthoquinone derivative can be obtained by a reaction of 1,2-naphthoquinone-4-sulfonyl or 1,2-naphthoquinone-5-sulfonyl with a hydroxyl group-containing compound.
The hydroxyl group-containing compound may be a mono- or polyhydric alcohol, or a phenol having at least one hydroxyl group. Examples of the phenol other than the above-mentioned phenols are hydroquinone; resorcin; phloroglucin; alkyl esters of gallic acid, 2,4-dihydroxybenzophenone; 2,3,4-trihydroxybenzophenone; tetrahydroxybenzophenones (e.g., 2,3,3xe2x80x2,4-tetrahydroxybenzophenone, 2,3,4,4xe2x80x2-tetrahydroxybenzophenone, 2,2xe2x80x2,4,4xe2x80x2-tetrahydroxybenzophenone); pentahydroxybenzophenones (e.g., 2,3,3xe2x80x2,4,4xe2x80x2-pentahydroxybenzophenone, 2,3,3xe2x80x2,4,5xe2x80x2-pentahydroxybenzophenone); polyhydroxytriphenylmethanes such as tri- or tetrahydroxytriphenyl-methane [e.g., (3,4-dihydroxybenzylidene)bis(2-t-butyl-5-methoxyphenol), (3,4-dihydroxybenzylidene)bis(2-cyclohexyl-5-methoxyphenol), (3,4-dihydroxybenzylidene)bis(2-t-butyl-4-methoxyphenol), (3,4-dihydroxybenzylidene)bis(2-cyclohexyl-4-methoxyphenol)]; and polyhydroxyflavans (e.g., 2,4,4-trimethyl-2xe2x80x2,4xe2x80x27-trihydroxyflavan, 2,4,4-trimethyl -2xe2x80x23xe2x80x24xe2x80x27,8-pentahydroxyflavan, 6-hydroxy-4a-(2,4-dihydroxyphenyl)-1,2,3,4,4a,9a-hexahydroxanthene -9-spiro-1xe2x80x2-cyclohexane).
An aromatic azide compound is usually used as the azide compound. Examples of the azide compound are monoazide compounds [e.g., 2,6-dichloro-4-nitro-1-azidobenzene, N-(4-azidophenyl)-N-phenylamine, N-(4-azidophenyl)-N-(4-methoxyphenyl)amine, 1-azidopyrene]; diazido compounds [e.g., 3,3xe2x80x2-dimethyl-4,4xe2x80x2-diazidobiphenyl, 3,3xe2x80x2-dimethoxy-4,4xe2x80x2-diazidobiphenyl, 4,4xe2x80x2-diazidodiphenylmethane, 4,4xe2x80x2-diazido-3,3xe2x80x2-dichlorodiphenylmethane, 4,4xe2x80x2-diazidodiphenylether, 4,4xe2x80x2-diazidodiphenylsulfone, 3,3xe2x80x2-diazidodiphenylsulfone, 4,4xe2x80x2-diazidodiphenylphosphide, 4,4xe2x80x2-diazidobenzophenone, 4,4xe2x80x2-diazidostilbene, 4,4xe2x80x2-diazidochalcone, 2,6-di(4-azidobenzal)cyclohexanone, 2,6-di(4-azidobenzal)-4-methylcyclohexanone, 2,6-di(4-azidocinnamylidene)cyclohexanone, N,N-di(4-azidophenyl)amine]; and polyazide compounds. These azide compounds can be used singly or as a combination of two or more.
Suitable as the azide compound are those efficiently generate nitrogen gas upon photoirradiation and form nitrene. For an increased crosslinking efficiency with the base resin (e.g., novolak resins, polyvinylphenol-series polymers), diazide compounds are preferable.
As the photoactive acid generator, various compounds that show large absorption at wavelength xcex1 or xcex2 (large absorbance at xcex1 or xcex2) and efficiently generate an acid (e.g., a protonic acid or a Lewis acid) upon exposure to a light of wavelength xcex1 or xcex2 are available and examples of which are sulfonic esters and Lewis acid salts that will be mentioned below. 
The acid generator generates an acid upon photoirradiation and accelerates the crosslinking of the base resin (e.g., in the case where a novolak resin is used as the base resin), or deprotects a protecting group upon exposure for pattern forming (e.g., in the case where the base resin is a polyvinylphenol resin) and therefore is effective for making the patterned areas of the base resin (a positive-type resin) readily alkali-soluble.
As the crosslinking agent, various crosslinking agents that accelerate the crosslinking of the base resin with the aid of an acid generated by the acid generator can be used, and examples of which are amino resins, particularly meramine derivatives. The meramine derivatives include methylolmelamines (e.g., hexamethylolmelamine); alkoxymethylmelamines (e.g., C1-4alkoxymethylmelamines such as hexamethoxymethylmelamine); condensates thereof; and co-condensates with co-condensable components (e.g., urea, benzoguanamine).
When a polyvinylphenol-series polymer is employed as a positive-type photosensitive resin, the first photoactive ingredient can be constituted of an azide compound and the second photoactive ingredient can be constituted of a photoactive acid generator. As the azide compound and the photoactive acid generator, use can be made of the above-mentioned azide compounds and the acid generators, respectively.
The amount of the first photoactive ingredient can be selected from the range of, for example, 0.01 to 100 parts by weight (e.g., 1 to 100 parts by weight), preferably about 0.05 to 100 parts by weight (e.g., 10 to 100 parts by weight), and more preferably about 0.1 to 80 parts by weight (e.g., 20 to 80 parts by weight) relative to 100 parts by weight of the base resin, depending on the species of the base resin or that of the photoactive ingredient.
The amount of the second photoactive ingredient can be selected from the range of, for example, about 0.0001 to 10 parts by weight (e.g., 0.01 to 10 parts by weight), preferably about 0.0005 to 7 parts by weight (e.g., 0.05 to 7 parts by weight), more preferably about 0.001 to 5 parts by weight (e.g., 0.1 to 5 parts by weight), and particularly about 0.001 to 2 parts by weight relative to 100 parts by weight of the base resin, depending on the species of the base resin or that of the photoactive ingredient. For example, the amount of the azide compound is about 0.01 to 5 parts by weight, preferably about 0.05 to 3 parts by weight, and more preferably about 0.1 to 2 parts by weight (e.g., 0.1 to 1.5 parts by weight), relative to 100 parts by weight of the base resin (a novolak-series resin). The amount of the acid generator is about 0.01 to 3 parts by weight (e.g., 0.01 to 1 part by weight), preferably about 0.02 to 2 parts by weight (e.g., 0.02 to 1 part by weight), and more preferably about 0.02 to 1 part by weight (0.02 to 0.5 part by weight) relative to 100 parts by weight of the base resin. The amount of the crosslinking agent is about 0.05 to 5 parts by weight (e.g., 0.05 to 3 parts by weight) and preferably about 0.1 to 3 parts by weight (e.g., 0.1 to 1.5 parts by weight), relative to 100 parts by weight of the base resin. Moreover, when employing a polyvinylphenol-series polymer as the base resin, the amount of the azide compound is about 0.01 to 5 parts by weight (e.g., 0.05 to 3 parts by weight), preferably about 0.1 to 2 parts by weight, and more preferably about 0.1 to 1 part by weight relative to 100 parts by weight of the base resin, and the amount of the acid generator is about 0.0001 to 1 part by weight, preferably about 0.0005 to 0.1 part by weight, and more preferably about 0.001 to 0.01 part by weight.
The aforementioned photosensitive resin composition can be produced by mixing a base resin with a plurality of photoactive ingredients each having an absorption range at wavelength xcex1 or xcex2, the wavelengths thereof being different from each other. If an existing photosensitive resin composition already containing the first or second photoactive ingredient is to be used, what is needed to provide the photosensitive resin composition of the present invention is merely to add the second photoactive ingredient or the first photoactive ingredient thereto.
To the photosensitive resin composition may be added an alkali-soluble component such as an alkali-soluble resin, a dye, a solvent, etc. As the solvent, use can be made of, for example, hydrocarbons, halogenated hydrocarbons, alcohols, esters, ketones, ethers, cellosolves, carbitols, glycol ether esters (e.g., cellosolve acetate, propylene glycol monomethyl ether acetate), and mixed solvents thereof.
Moreover, a purified resin component previously fractionated based on, for example, the molecular weight may be used as the base resin, and from the photosensitive resin composition may be removed impurities by using a conventional separation-purification means such as filter.
According to the method of the present invention, the photosensitive resin composition is coated on a substrate (e.g., silicon wafer) and dried. Thereafter, the coating layer (resist film or layer) was exposed to a light of a wavelength of either xcex1 or xcex2 through a given mask to form a pattern, followed by overall-exposure to a light of the other wavelength and development. Thus, there can be formed a pattern of high resolution.
After applying the photosensitive resin composition on the substrate, the coating layer may be soft-baked with a heating means such as a hot plate at a suitable temperature (e.g., 80 to 100xc2x0 C.) for a suitable period of time (e.g., 1 to 2 minutes) so that a solvent is evaporated.
For the patterning exposure (imaging exposure) or the overall exposure, lights of various wavelengths can be used according to the species of the base resin, and the light may have either a single wavelength or a compound wavelength. For the exposure, g-line (e.g., 436 nm), i-line (365 nm), excimer laser [e.g., XeCl (308 nm), KrF (248 nm), KrCl (222 nm), ArF (193 nm), and ArCl (172 nm)] can usually be employed with advantages. Examples of the preferred excimer laser include KrF, KrCl, ArF, and ArCl excimer lasers. Preferably, the imaging exposure is conducted with a light of a single wavelength, and g-line (436 nm), i-line (365 nm) or excimer laser can be used for a resist for semiconductor production. The patterning exposure or patternwise exposure can be carried out according to a conventional method, in which the exposure is done through a given mask to form a predetermined pattern. After the patternwise exposure, if needed, the pattern may be baked using a heating means such as a hot plate at a suitable temperature (e.g., 100 to 120xc2x0 C.) for a suitable period of time (e.g., 1 to 2 minutes).
The exposing wavelength for pattern forming differs for the species of the base resin or the photoactive ingredients used, and the wavelength may be the shorter one (xcex2) or the longer (xcex1). Usually, when a light of the shorter wavelength is used for the imaging exposure, the overall exposure is conducted with a light of the longer wavelength. And, when a light of the longer wavelength is used for the imaging exposure, the overall exposure is mostly carried out with a light of the shorter wavelength. For example, when using a novolak resin as the base resin, the coating layer can be image-exposed to a light of wavelength xcex1, followed by an overall exposure to a light of wavelength xcex2. Moreover, when using for example a polyvinylphenol-series polymer as the base resin, the coating layer can be image-exposed to a light of wavelength xcex2, followed by an overall exposure to a light of wavelength xcex1. In either case, to form a layer hardly soluble or readily soluble in a developer (developing solution) on the surface of a photosensitive layer by overall exposure, a photoactive ingredient active at the wavelength of the light of the overall exposure is desired to be substantially inert at the wavelength of the light of the imaging exposure. Moreover, a photoactive ingredient which is activated by the light of the wavelength for the imaging exposure is preferred to be substantially inert at the wavelength of the light used for the overall exposure.
The overall exposure of the surface of the photosensitive resin composition of the present invention after the imaging exposure makes the surface of the photosensitive layer hardly soluble when the resist is of positive-type and readily soluble when the resist is of negative-type, depending on whether the resist is of positive-type or negative-type.
According to, e.g., the type of the resist to be formed and the species of the second photoactive ingredient, the energy for the overall exposure can be selected from a suitable range within which the surface can be treated so as to be hardly soluble or readily soluble of, for example, about 0.05 to 50 mJ/cm2, preferably about 0.1 to 25 mJ/cm2, and more preferably about 0.5 to 25 mJ/cm2. Moreover, when the overall exposure is conducted using the excimer laser, the energy for the exposure can be selected from within the range of, e.g., about 0.5 to 50 mJ/cm2 and preferably about 1 to 25 mJ/cm2. Furthermore, in a conventional process for pattern forming in which a 20 xcexcm-thick photosensitive layer containing no particulate is exposed and the exposed areas or non-exposed areas are dissolved with a developing agent to form a pattern (e.g., resist pattern), the exposure energy for making the surface of the photosensitive layer water-repellent or hardly soluble can be selected from the range of about 1 to 20 and preferably about 1 to 10, assuming the exposure energy needed for pattern forming (mJ/cm2) to be 100. The surface can be made water-repellent or hardly or slightly soluble also by controlling the photoirradiation time or the intensity of light.
After the overall exposure, a predetermined pattern can be formed by developing according to a conventional method using a developer such as an alkaline developer. After the development, if needed, the formed pattern may be post-baked utilizing a heating means such as a hot plate at a suitable temperature (e.g., 120 to 130xc2x0 C.) for a suitable period of time (e.g., 1 to 2 minutes).
According to the present invention, the resolution can be improved without employing an exposure light at a shorter wavelength. In further detail, a light for imaging exposure irradiated on a photosensitive material through a mask does not show an accurate rectangular light distribution corresponding to the mask, but is xe2x80x9cvaguexe2x80x9d due to the diffraction and turning of the light. Thus, a pattern on a positive-type photosensitive material is made angular like a triangle. In the case of a negative-type photosensitive material, since the surface of strong light absorption is preferentially cured, a pattern is made in a T-shape. Therefore the resolution is deteriorated. In contrast, since overall exposure after patternwise exposure makes the surface of a resist layer of a positive-type photosensitive material hardly or slightly soluble, dissolution of the surface of the resist layer of strong light absorption is inhibited. In a negative-type photosensitive material, the surface of a resist layer is made readily soluble (in other words, the formation of a layer having the surface hardly soluble is inhibited), leading to an acceleration in the developability of the surface. Thus, a pattern having a rectangular cross section is formed with a pattern profile of high contrast (xcex3-value) and the resolution largely improved. Moreover, even when the patternwise exposure is done slightly out of focus, the above-mentioned step of making the surface of the resist layer hardly soluble or readily soluble improves the resolution, consequently resulting in a significant improvement in focus latitude.
Furthermore, according to the present invention, sensitivity also is substantially improved. To give an example, in a negative-type photosensitive material utilizing radical polymerization system for curing, inhibition of curing due to oxygen in the air is observed. However, the addition of an acid generator and a crosslinking agent as the second photoactive ingredients accelerates the curing of the surface on overall exposure, substantially improving the sensitivity. On the other hand, in a positive-type photoactive material, resolution and sensitivity are incompatible with each other. Therefore, it is usually difficult to hold both at high levels. However, since the present invention can largely improve the resolution without deteriorating the sensitivity, it can be said that the sensitivity also is substantially improved.
Furthermore, according to the present invention, the hydrophilicity and the hydrophobicity of the surface of a photosensitive material are controllable, and therefore, uniformity in development can be improved. Recently, especially in the field of resist, there is a growing trend toward making resist layers hydrophobic along with improvements in performance. Thus, the wettability with an alkaline developer is deteriorated and, particularly with a substrate having a large area, the developer hardly spreads out uniformly over the entire surface of the substrate, which results in a failure in development with uniformity. According to the present invention, however, in the case of a positive-type material in which only the exposed areas are made hydrophilic, for example, a material which generates an acid upon irradiation of a light of wavelength xcex2 is previously added and an overall exposure with a light of wavelength xcex2 is conducted to generate an acid only near the surface and make the surface hydrophilic, thereby improving the wettability of the non-exposed areas.
According to the present invention, since the photoactive component comprises a plurality of photoactive ingredients as a combination sensitive to lights of different wavelengths, sensitivity and resolution can largely be improved even with existing equipment (particularly, exposure system). Moreover, pattern profile and focus latitude can be improved to a large extent. Therefore, the present invention has various applications and can be used as, e.g., materials for forming circuits (e.g., resists for semiconductor production, printed-wiring boards), imaging materials (e.g., printing plate materials, materials for relief printing), and so on. Especially, for being capable of achieving high sensitivity and resolution, the present invention can advantageously be used for resists for semiconductor production.